GB2180841A

GB2180841A - Aqueous coating composition

Info

Publication number: GB2180841A
Application number: GB08615988A
Authority: GB
Inventors: Toshiharu Nakaya; Akimitsu Uenaka; Takanobu Ueda
Original assignee: Nippon Paint Co Ltd
Current assignee: Nippon Paint Co Ltd
Priority date: 1983-06-18
Filing date: 1986-07-01
Publication date: 1987-04-08
Also published as: GB2144127A; DE3422564A1; FR2547592B1; FR2547592A1; JPS601266A; GB2144127B; US4588759A; JPH033713B2; DE3422564C2; GB8615988D0; GB8415450D0; CA1258331A

Description

1

GB2 180841A 1

SPECIFICATION

Aqueous coating composition

5 The present invention relates to an aqueous coating composition and more specifically, an aqueous coating composition with excellent storage stability and the like. The invention also concerns the preparation of said composition.

An aqueous coating composition comprising resinous powder uniformly dispersed in an aqueous resin solution is, because of its well balanced characteristics of good flowability due to the 10 aqueous resin and capability of forming a thicker film due to the powdered resin, free from the generic drawback possessed by the aqueous resin of sagging and capable of resulting excellent pinhole resistance, and hence far surpasses others in the application characteristic thereof. However, in such a powdered resin dispersion type aqueous coating composition, there is indeed an excellent application characteristic at an earlier stage, but is a serious problem of 15 lowering in pinhole resistance, one of the important features of application characteristic, afer storing at an elevated temperature, of the composition.

To solve the question of this change of stability with time at an elevated temperature, the inventors have devoted deep studies into the subject, and found that when carboxyl bearing resin is selected as powder forming resin and combined with basic pigment and base neutralized 20 aqueous resin, thereby masking the carboxyl groups of said powdered resin with the said basic pigment and making them inert in the system, is obtained a coating composition which is excellent in high temperature stability with time and storage stability without the deterioration of application characteristics thereof. On the basis of these findings, Japanese Patent Application No. 73674/82 was filed on April 30, 1982. According to the said invention, both storage 25 stability and pinhole resistance with time of the resinous powder dispersion type aqueous coating composition are indeed improved, but further improvements are still needed in both respects.

Under the circumstances, the inventors, having made endeavor to get the same, have found that if the water insoluble resin is composed of considerably higher molecular weight polymer by 30 the adaption of particular means wherein a specific type of resin is treated with amine, swelling dissolution of such resinous powder in the system with time is effectively controlled, and high temperature stability with time of the resulted coating composition is markedly improved because of the improvement in viscoelastic change and effective control of the curing speed thereof.

Having further developed the invention of said Japanese Patent Application No. 73674/82, the 35 inventors have also found that if the masking amine for the carboxyl bearing resin is selected from the member having a higher boiling temperature, the curing speed is effectively and advantageously controlled, thereby giving particularly excellent application characteristics and curing property of the composition. Of course, the combination of the abovesaid two inventions may give particularly good results in respect of storage stability, application characteristics and 40 curing property and the like.

On the basis of these findings, the present inventions have been made.

Thus, in accordance with the invention, is provided an aqueous coating composition comprising water insoluble resinous powder, base neutralization type aqueous resin, pigment and other optional additives including hardner, characterized by that said water insoluble resinous powder is 45 composed of polymer obtained by reacting a mixture of epoxy resin and a resin having both epoxy groups and epoxy reactive functional group, or a resin having both epoxy group and epoxy reactive functional group, with an amine in an amount which is sufficient enough to cause ring-opening of 10 to 50% of the total epoxy groups.

The invention also provides an aqueous coating composition comprising carboxyl bearing 50 resinous powder (I), basic compound (II), aqueous resin (III) and optional other additives including the compound (IV) which is reactive with said (I) and/or (III), the amount of said basic compound being 0.3 to 1.2 equivalent to the total amounts of carboxyl groups of (I) and (III) and the solid weight ratio of (I): (III) being 2:98 to 98:2, characterized by that at least 20% of said basic compound (II) is the member having a boiling temperature of more than 150°C. 55 The invention also provides an aqueous coating composition as stated in the first type of invention which is characterized by that an amine having a boiling point of 150°C and more is used as the said amine to be reacted with the epoxy groups and/or neutralization purpose of the aqueous resin.

The resinous powder used in the present invention is composed of polymer obtained by 60 reacting a mixture of epoxy resin and a resin having epoxy reactive functional group, or a resin having both epoxy group and epoxy reactive functional group, with an amine in an amount which is sufficient enough to cause ring-opening of 10 to 50% of the total epoxy groups.

As the epoxy resins, various type of resins have been known including such member as being prepared by the reaction of bisphenol A and epichlorohydrin, and any of the members may 65 satisfactorily be used for the purpose of this invention.

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GB2 180841A 2

Most typical members of the resin having epoxy reactive functional groups are, for example, acrylic resin and polyester resin each having carboxyl groups, and however, the invention shall not be limited to these members only and any of the resins having epoxy reactive functional group as amino, imino, acid amide or the like may satisfactorily be used. As an example of the 5 resin having both epoxy group and epoxy reactive functional group (e.g. carboxyl group), mention is made of epoxy modified acrylic resin like Finedic A 217 manufactured by Dainippon Ink Co., Ltd., which is also advantageously used as resinous powder constituting polymer of this invention.

In order to simplify and assist easy understanding of the invention, explanation shall be given 10 with the resinous powder composed of epoxy resin and carboxyl containing acrylic resin. Since the reaction rate of epoxy resin with carboxyl containing acrylic resin is rather poor, the mere mixe-melting is insufficient to obtain the desired highly polymerized product. However, when an amine is present in the system, there occurs ring-opening of epoxy group and results a highly polymerized resin through polycondensation of epoxy resin per se or reaction with carboxyl 15 bearing acrylic resin.

In the present invention, use is made of resinous powder of such highly polymerized, water insoluble resin obtained by the reaction of a mixture of epoxy resin and a resin having epoxy reactive functional group, or a resin having both epoxy group and epoxy reactive functional group, with an amine, the amount of said amine being sufficient enough to cause ring-opening of 20 10 to 50% of the total epoxy groups contained.

Usually, it has been known in the art that melt-mixing of epoxy resin and carboxyl bearing acrylic resin will give only limitted extent, e.g. 3 to 5%, of ring-opening of the contained epoxy groups. With such extent of ring-opening, the present polymerization effect cannot be expected therewith. When an amine is added to the system, the extent of said ring-opening of epoxy 25 groups is increased proportionally with the increase in said amine quantity.

However, too excessive amine is not recomended because if the ring-opening exceeds over 50% of the total epoxy groups, there results an excessively polymerized product, which is inadequate in attaining the object of the invention due to the formation of granulations in the composition and difficult dispersion thereof. Thus, the inventors have found that when the epoxy 30 ring-opening rate is within 10 to 50% of the total epoxy groups, an optimum coating composition with good dispersion property and storage stability may be obtained, and most preferably, epoxy ring-opening rate is 15 to 30% of the total epoxy groups. On the basis of these findings, the present invention has been made.

The abovementioned resinous powder used in the present invention may advantageously be 35 prepared by mixing, for example, epoxy resin and epoxy reactive functional group bearing resin, e.g. carboxyl bearing acrylic resin, each in powder form, and after adding with an amount of amine, subjecting to melt-mixing atherof.

At this time, the amine amount is determined so as to give 10 to 50% epoxy ring-opening rate calculated by the formula:

40

A-B

x 100

A

45 wherein A stands for the amount of epoxy groups in the composition of epoxy resin and epoxy reactive functional group bearing resin, and B is the amount of epoxy groups in the final product obtained by melt-mixing the abovesaid two resins and amine.

After cooling, the product is pulverized and shieved to obtain the powder whose mean diameter is less than 300//. The thus obtained powder is desirably dispersed in an aqueous 50 medium. In the final aqueous coating composition, the resinous powder may have in general a mean diameter of 0.3 to 40fi and however, this is not essential in the invention and any powders having a more fine particle size may be likewise useful. In any way, the mean diameter may be selected appropriately within a range customarily used in the art concerned. Thus, the abovementioned reaction product may be further pulverized by mechanical means as, for 55 example, fluid energy mill and thus obtained fine powder may be added to an aqueous medium.

As regards temperature at which the abovementioned resins and amine are melted together, it may appropriately be selected depending essentially on the type of resinous component. For example, in the case of combination of epoxy resin and carboxyl bearing acrylic resin, it is generally determined in a range of 90 to 110°C.

60 As an amine component, no particular requirements are needed. However, if the boiling point of the employed amine is lower than the abovesaid melting temperature, there is a fear the amine will dissipate out of the system during said reaction and consequently, some effective controlling means or employment of larger quantity of amine is essential in that case and thus the reaction control will become difficult to do. Therefore, it is preferred to use an amine with 65 much higher boiling point as compared with the above said melting temperature.

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65

GB2 180841A

The inventors have also found that particularly preferred members are such amines as being solid at room temperatures and having a comparatively higher boiling point as, for example,

aliphatic monoamines having more than 12 carbon atoms.

In the present invention, the abovesaid resinous powder(s) is (are) used together with base 5 neutralization type aqueous resin and pigment. 5

Examples of said base neutralization typoe aqueous resin used in the present invention are alkyd resin, polyester resin, maleic oil resin, maleic polyalkadiene resin, epoxy resin, acrylic resin, urethane resin and the like.

Introduction of carboxyl groups in particular resin may be carried out in a conventional way as, 10 for example, selection of appropriate monomers to be polymerized, control of polymerization 10

reaction and the like.

More specifically, in the case of alkyd and polyester resins, carboxyl groups may be introduced into the resins at the stage wherein polybasic acid and polyhydric alcohol are reacted each other.

In the case of maleic oil resins, carboxyl groups may be advantageously introduced at the time 15 when drying oil (linseed oil, castor oil, soya-bean oil, tung oil) is treated with maleic anhydride. 15

In the case of maleic polyalkadiene resins, carboxyl groups may be introduced by the addition of polybutadiene (e.g. 1,2-polybutadiene, 1,4-polybutadiene, 1,2- and 1,4-copolymerized polybu-tadiene), polyisoprene or polycyclopentadiene, with unsaturated carboxylic acid, (e.g. maleic anhydride, hymic anhydride, fumaric acid, itaconic acid).

20 As the epoxy resins, use can be made of various type typiocally exemplified by the reaction 20 product of bisphenol A and epichlorohydrin, as well as various compounds with epoxy groups.

Some of these resins are water soluble in nature and they are directly used as aqueous resins. If less soluble, acidic groups may be introduced into a part or whole oxirane groups, thereby making them water soluble. In the case of acrylic resins, they may be prepared by copolymeriz-25 ing a,/?-unsaturated carboxylic acid (e.g. acrylic acid, methacrylic acid, cinnamic acid, crotonic 25 acid, fumaric acid, citraconic acid, maleic anhydride) and acrylic ester (e.g. methyl, ethyl, propyl,

butyl, hexyl, lauryl ester) and/or methacrylic ester (e.g. methyl, ethyl, propyl, butyl, hexyl, lauryl ester), and if required, other polymerizable monomers.

In the case of urethane resins, use can be made of the products having as skeletal structure, 30 dissocyanate compound (e.g. hexamethylene diisocyanate, tolylene diisocyanate, xylylene diisocy- 30 anate, 4,4'-methylene bis(cyclohexyl isocyanate), isophorone diisocyanate).

For the solubilization of such aqueous resin in an aqueous medium, the abovesaid carboxyl groups may be neutralized with a basic material (e.g. monomethylamine, dimethylamine, trimethy-lamine, monoethylamine, diethylamine, triethylamine, monoisopropylamine, diisopropylamine, di-35 ethylene triamine, triethylene tetramine, monoethanolamine, diethanolamine, triethanolamine, mo- 35 noisopropanolamine, diisopropanolamine, dimethylethanolamine, morpholine, methyl morpholine, piperazine, ammonia, sodium hydroxide, potassium hydroxide, lithium hydroxide.)

Preferably said basic material may also be an amine having a higher boiling point of 150°C and more.

40 As the pigment, any of the members customarily used in paint area, may be satisfactorily 40

used.

In the present invention, is provided an aqueous coating composition comprising abovesaid resinous powder, aqueous resin and pigment, uniformly dispersed in an aqueous medium. The said aqueous medium (preferably deionized water) may contain a small amount of water-miscible, 45 organic solvent as, for example, ethyleneglycol monomethyl ether, ethyleneglycol monoethyl 45

ether, ethyleneglycol monobutyl ether, methanol, ethanol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, t-butyl alcohol, dimethyl formamide and the like.

In the present coating composition, the abovesaid resinous powder and aqueous resin are compounded in solid weight ratio of 2:98 to 98:2, preferably 2:98 to 60:40.

50 If the amount of said resinous powder is excessively lower order, there is a trend that 50

application characteristic will get worse, whereas if it is of excessively higher order, then a trouble of inferior flowability.

It has also been found that at the level of 40 wt% and more of the aqueous resin in the total resin, particularly good results are obtained in respect of application characteristics, coating 55 appearance and gloss. 55

In the present coating composition, it may also be contained as desired, a compound which is reactive with the water insoluble resinous powder and/or aqueous resin, that is, hardening agent. Examples of such compounds are melamine resin, polyvalent metal salt (e.g. cobalt naphthenate,

lead naphthenate, zinc naphthenate), triglycidyl isocyanurate (TGIC), dicyandiamide and the like. 60 When added, its compounding ratio is, in terms of solid weight ratio, determined so as to be 60 less than 4 times the amount of water insoluble resin and/or aqueous resin. By the adoption of such hardening agent, it may be obtained a coating with far improved film performance because of the occurence of cross-linking reaction in the heat-curing step.

The present composition may further include other conventional additives as modifying agent, 65 dispersing aid, surface regulator and the like, as desired. 65

4

GB2 180841A 4

The present coating composition may be advantageously prepared by compounding the above-mentioned components in any known manners and mixing well to obtain a uniform dispersion. In a preferred embodiment, the present aqueous coating composition may be prepared by mixing a combination of epoxy resin and epoxy reactive functional group bearing resin, or a resin having 5 both epoxy group and epoxy reactive functional group, with an amine, melting the same to 5

effect ring-opening of 10 to 50% of the epoxy groups contained, pulverizing thus obtained reaction product and shieving to obtain fine particles having a mean diameter of less than 300//,

mixing and dispering the fine powder in an aqueous medium containing base neutralization type aqueous resin, and compounding the mixture with pigment and other optional additives including 10 hardening agent. ^10

In one other embodiment, the present coating composition may be prepared by adding to the abovementioned reaction product of said resin(s) and amine, with pigment, melting the same to obtain mixed powder, pulverizing the same by means of fluid energy mill to fine powder of less than 50//, and finally dispersing the fine powder into an aqueous medium containing base 15 neutralization type aqueous resin by means of disper at 40°C or less. 15

Thus obtained aqueous coating composition of this invention do possess the characteristics of high solid coating composition comprising aqueous resin and resinous powder and is characterized by having far improved storage stability and elevated temperature-longer time stability and pinhole resistance of the coating.

20 As already stated, in the most preferred embodiment of the invention, the amine substance 20 used for the reaction with epoxy groups for the purpose of higher polymerization of water insoluble resin and for the reaction with aqueous resin for neutralization purpose of said resin should preferably be a member having a higher boiling point of 150°C and more, most preferably 150~400°C.

25 In this case, particularly excellent results in respect of storage stability and application charac- 25 teristics may be obtained because of the combination characteristics of highly polymerized water insoluble resin powder and controlled vaporization of the used amine from the aqueous resin.

The latter feature may give good affect on curing property of the coating composition.

In the second aspect of this invention, is provided an aqueous coating composition comprising 30 carboxyl bearing resinous powder, basic compound and aqueous resin and being excellent in 30

storage stability and application characteristics (pinhole resistance and sagging resistance), which is characterized by that at least 20% of said basic compound is the member having a high boiling temperature of more than 150°C, preferably 150 to 400°C.

In this invention, the most characteristic feature resides in the employment of high boiling 35 basic compound for the masking of carboxyl groups of resinous powder, as well as the 35

solubilization of aqueous resin.

Examples of such members are diethylethanolamine (B.p. 163°C), 2-(dimethylamino)-2-methyl-propanol (DMAMP, 160°C), diisopropanolamine (249°C), dimethyl-2-(2'-hydroxyethoxy)ethylamine (DMAEE, 200°C), aminoethyl ethanolamine (244°C), diethanolamine (268°C), and triethanolamine 40 (360°C). 40

As the carboxyl bearing resinous powder (I), mention is made of, for example, polyester resin and acryl resin, which are well known in the art. The grain size of the powder may affect on time-stability and application characteristics of the composition and appearance of the coating thereof and it is usually selected in a range of 3 to 60//, preferably 5 to 25//. The resinous acid 45 value is usually 15 to 300, preferably 30 to 100. If the resinous acid value is lower than the 45 abovementioned range, then it is unable to expect an effective crosslinking, curing reaction,

whereas if too higher, then there remains a considerable quantities of free carboxyl groups in the coating, which will affect undesirably on water resistance after all.

The invention shall be now more fully explained in the following Examples. Unless otherwise * 50 being stated, all parts are by weight. 50

Example 1 (Method )

(1) Preparation of resinous powder:

8 Parts of Finedic M-6103 (polyester resinous powder, manufactured by Dainippon Ink Co.,

55 acid value 70, Tm 110°C, molecular weight 3000, particle size less than 104//), 8 parts of 55

Epicoat # 1004 (epoxy resinous powder, manufactured by Shell Co., epoxy equivalent 1000,

molecular weight 1400), 10 parts of BF-10 (precipitated barium sulfate pigment, manufactured by Sakai Kagaku) and 0.32 part of lauryl amine were mixed and fused together in Ko-kneader at 110°C. After cooling, the product was pulverized and shieved to obtain powders having a mean 60 diameter of less than 105//. Epoxy ring-opening rate of this powdered resin is shown in Table 1. 60

(2) Preparation of powder paste:

52 Parts of resinous powder obtained in (1), 42 parts of aqueous polyester resin varnish (acid value 55, hydroxyl number 35, molecular weight 1360, employed neutralizing agent dimethyleth-65 anolamine, neutralization rate 80%, non-volatile content-50 wt%, pH 6.6) and 30 parts of 65

5

GB2 180841A 5

deionized water were uniformly mixed together and dispersed in Disper at. 70°C for 15 minutes to obtain a stable dispersion of fine resinous powder (less than 30p, measured by grindometer. Method A).

5 (3) Preparation of pigment paste:

42 Parts of the same aqueous polyester resin varnish as used in the preceding paragraph (2), 30 parts of deionized water and 52 parts of Titanium R-820 (titanium oxide pigment, manufactured by Ishihara Sangyo K.K.) were mixed and dispersed well in Paint Conditioner with glass beads, for 30 minutes to obtain a pigment paste (viscosity 86 Ku/25°C, grain size less than 10 10/i, measured by grindometer. Method A)

(4) Preparation of aqueous coating composition:

124 Parts of the powder paste of paragraph (2) and 125 parts of the pigment paste of paragraph (3) were uniformly mixed together and then added with 20 parts of Cymel 300 15 (melamine resin, manufactured by Mitsui Cyanamide Co.).

The weight ratio of resinous powder/water soluble polyester resin was 43/57.

(5) Coating test:

The coating composition of the preceding paragraph (4) was diluted with pure water to #4 20 Ford Cup viscosity of 30 sec./20°C.

Each aliquot portion of the diluted composition was, immediately after dilution, after storing at 40°C for 10 days, at 40°C for 20 days, and at 40°C for 30 days, applied by spraying on a steel plate, set for 5 minutes and baked at 150°C for 30 minutes.

The maximum film thickness showing resistance against the generation of pinholes for the 25 respective composition was measured and shown in Table 1.

Example 2

The same procedures as stated in Example 1 were repeated excepting using 0.48 part of stearyl amine (as amine in the powdered resin) in place of 0.32 part of laurylamine, to obtain an 30 aqueous coating composition.

Example 3

The same procedures as stated in Example 1 were repeated excepting using 0.16 part of hexylamine (as amine in the powdered resin) in place of 0.32 part of laurylamine, to obtain an 35 aqueous coating composition.

Example 4

The same procedures as stated in Example 1 were repeated excepting using 0.16 part of dodecamethylene diamine (as amine in the powdered resin) in place of 0.32 part of lauryl amine, 40 to obtain an aqueous coating composition.

Example 5

The same procedures as stated in Example 1 were repeated excepting using 0.32 part of DMAEE (dimethyl-2-(2'-hydroxyethoxy)ethylamine) (as amine in the powdered resin) in place of 45 0.32 part of laurylamine, to obtain an aqueous coating composition.

Comparative Example 1

(1) Preparation of resinous powder:

Resinous powder was prepared as in Example 1 using 8 parts of Finedic M 6103 and 8 parts 50 of Epicoat # 1004, but not BF-10 and laurylamine.

(2) Preparation of powder paste:

Powder paste was prepared as in Example 1 but using 32 parts of the resinous powder of the preceding paragraph (1).

55

(3) Preparation of pigment paste:

The same pigment paste as stated in example 1 was used.

(4) Preparation of aqueous coating composition:

60 From 104 Parts of the powder paste of (2), 126 parts of pigment paste of (3) and 20 parts of Cymel 300, an aqueous coating composition was prepared as in Example 1.

(5) Coating test:

The similar coating test as stated in Example 1 was carried out.

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GB2 180841A 6

Comparative Example 2

An aqueous coating composition was prepared as in Example 1 but using 8 parts of Finedic M 6103, 8 parts of Epicoat # 1004 and 10 parts of BF-10 only.

5 Comparative Example 3 5

An aqueous coating composition was prepared as in Example 1 but using 8 parts of Finedic M 6103, 8 parts of Epicoat #1004, 10 parts of BF-10 and 0.06 part of laurylamine.

Comparative Example 4

10 (1) Preparation of resinous powder: 10

8 Parts of Finedic M 6103, 8 parts of Epicoat #1004, 10 parts of BF-10 and 0.8 part of laurylamine were mixed and fused together in Ko-kneader at 150°C. After cooling, the product was pulverized and shieved to obtain resinous powder having a mean diameter of less than 105^.

15 15

(2) Preparation of powder paste:

The powder composition of (1) was subjected to dispersion procedure as in example 1, but since the grain size was more than 100/i (measured by grindometer. Method A), a stable dispersion could not be obtained. Even after the treatment in Paint Conditioner and fluid energy

20 mill, no good results were obtained. 20

Example 6 (Dispersion in Paint conditioner)

Powder paste was prepared as in Example 1 but using Paint Conditioner in place of Disper, for 50 minutes. A stable paste was obtained, grain size being less than 30/u (grindo meter Method 25 A). An aqueous coating composition was prepared as in Example 1 with this powder paste. 25

Example 7 (Jet mill)

Resinous powder was prepared as in Example 1 and then subjected to Jet mill to give grain size of less than 30/z.

30 30

Preparation of powder paste:

42 Parts of aqueous polyester resin varnish of Example 1 and 30 parts of deionized water were mixed together and to this were added gradually, while keep stirring, 52 parts of the resinous powder abovementioned, to obtain a stable paste having a mean grain size of less than 35 30fi (measured by grindometer. Method A). An aqueous coating composition was prepared with 35 this paste as in Example 1.

The similar test as stated in Example 1 was carried out with the respective coating composition given in Examples and Comparative Examples and the results obtained are shown in Table 1.

Table 1

Example solid weight ratio of resin.powder/aq. polyester resin epoxy resin ring — opening rate (%)

■axiaun film thickness (M)> no pinholes after dilution heating at 40°C for

10 days

20 days

30 days

1

43/57

20

60

55

50

2

43/57

18

65

60

55

50

3

43/57

19

60

50

45

40

4

43/57

16

58

53

45

40

5

43/57

24

55

50

40

6

43/57

20

55

52

50

45

7

43/57

20

60

58

55

48

Cob.Ex.1

43/57

4

50

20

less than 10

Cob.Ex.2

43/57

5

60

53

37

20

Cob.Ex.3

43/57

8

58

55

40

20

Cob.Ex.4

43/57

55

, —

—

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GB2 180841A 8

Reference Example 1

Preparation of pigment dispersion paste (1): To 46 g of aqueous resin varnish (1) shown in Table 2, were added 30 g of deionized water and 90 g of Rutile type titanium oxide pigment and the mixture was subjected to preliminary mixing and then to mix-dispersion in Paint condi-5 tioner at room temperature for 40 minutes with glass beads. Thus obtained paste was found to 5 be well dispersed and have the characteristics: grain size less than 10 fi4, Stormer viscosity 100Ku/25°C and non-volatile content 68%.

Example 8

10 Preparation of coating composition (1) 10

46 Grams of aqueous resin varnish of Table 2 were dissolved in 30 g of deionized water and to this, while keep stirring and heating, were gradually added 34 g of resinous fine powder (1) of Table 2 and the mixture was stirred well at 70°C for 15 minutes. A stable dispersion was obtained, whole neutralization rate was found to be 47%.

15 To the abovementioned dispersion liquid, were added 166 g of the pigment dispersion paste 15 of the Reference example 1 and 20 g of hexamethoxy methylol melamine (HMMM) and mixed well to obtain a coating composition. The characteristics of the composition were: non-volatile content 64 wt%, Stormer viscosity 110 Ku/25°C, and solid weight ratio of resinous fine powder/aqueous resin varnish 34/66.

CO

Table 2

aqueous resin varnish acid value

OH nunber base Material for neutraliz.

neutral. rate ( % )

NV

wt %

HV

(1) polyester resin

55

35

DHAMP

80

50

1360

(!') polyester resin

55

35

DME A

(2) ■ a 1 eic polybutadiene

95

—

DMEA

80

30

1200

(3) polyester resin

55

35

DEA

80

50

1360

(4) polyester resin

55

35

DMAEE

80

50

1360

(5) polyester resin

55

35

TEA

80

50

1360

(6) polyester resoin

55

35

aq. amnon ia

80

50

1360

O 00 to

00

o

00

CO

Table 3

resinous fine powder acid value grain size

H

(1) polyester resin

Finedic H 61 07 53 104>

■ anf. by Dainippon Ink Co., Ltd.

(2) polyester resin Finedic M 6103 manf. by Dainippon Ink Co., Ltd.

(3) epoxy resin Epicoat 1004

manuf. by Shell — 104>

Chea. Co. )

76

1 04 >

it o

Tg

°C

109

Ho lec. weight

3800

108

3000

100

1400

epoxy equiv,

925

a

DO NJ

00 O 00 .(*■

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GB2 180841A 11

Examples 9~16 and Comparative Examples 5~7

Coating compositions were prepared as in Example 8, using aqueous varnishes of Table 2 and resinous fine powders of Table 3, the details being shown in Table 4.

These compositions were stored at 40°C for 10 days and thereafter, subjected to stability test 5 and the results obtained were shown in Table 5. Application characteristics of these compo- 5

sitions on dull steel plates were also evaluated and the results were shown in Table 5.

In the abovementioned test, stability of the coating composition was evaluated from the following standards:

10 0 no abnormality 10

(viscosity change less than 5 Ku, no precipitation)

A.... increase in viscosity x precipitation

Table 4

Example

9

10

11

12

aq. varnish used

(1

')

(1

')

(1')

(1)

anounts (g)

46

deion. water(g)

30

resin, powder used

(0

(3)

(1)

(3)

(1)

(3) .

(2)

(3)

anounts (g)

24

10

24

10

15

19

24

10

basic compound

DMEA

anounts (g)

3

.4

1

.0

disper. tenp. x time

("C x mi nut.)

70 x

15

70 x

15

70 x

15

70 x

15

neutral, rate of total

carboxylic acids (%)

53

110

80

47

pigment disper. paste

aq. varnish used

(1)

(4)

(1)

anounts (g)

166

HMNM (g)

20

Coating composition

" non — volatile (wt%)

64

viscosity (Ku/25°C)

108

110

105

solid weight ratio

of resinous powder/

34/66

aq. resin varnish

Table 4 (continued)

Example

13

14

15

16

aq. varnish used

(1)

(2)

(4)

(1)

amounts (g)

46

76

46

deion. water(g)

30

0

30

resin, powder used

(1)

(3)

(1)

(4)

(1)

(3)

(1)

(3)

anounts (g)

12

10

24

10

24

10

24

10

basic compound

anounts (g)

disper. tenp. x time

(°C x ninut.)

60 x

15

60 x

15

60 x

15

50 x

15

neutral, rate of total

carboxylic acids (%)

64

53

pigment disper. paste

aq. varnish used

(1)

(3)

(1

')

(1)

anounts (g)

166

HMMM (g)

20

Coating composition

non —volatile (wt%)

62

64

viscosity (Ku/25t)

100

110

105

98

solid weight ratio

of resinous powder/

25/75

34/66

aq. resin varnish

Table 4 (continued)

Comparative Exaaple

5

6

7

aq. varnish used

(5)

(6)

(5)

amounts (g)

46

deion. water(g)

30

resin, powder used

(1)

(3)

(1)

(3)

anounts (g)

34

24

10

24

10

basic compound

—

TEA

anounts (g)

—

1.

1

disper. tenp. x tine

(T! x ninut.)

70 x 15

70 x

15

60 x

15

neutral, rate of total

carboxylic acids (%)

47

53

80

pignent disper. paste

aq. varnish used

(5)

(1')

(5)

anounts (g)

166

HMMM (g)

20

Coating coaposition

non —volatile (wt%)

64

viscosity (Ku/25"1C)

110

107

98

solid weight ratio

,

of resinous powder/

34/66

aq. resin varnish

G) DO N>

00

o

00

Ta b1o 5

coat, coaposition stabi lity *

■axiiun film thickness maxinui film thickness

exhibit, pinhole resis.

exhibit, sagging resist.

initial eIap. time initial elap. time

Example 8

©

55 \i

50 (i

70 n

65 n

9

o

60

70

10

©

65

60

55

60

1 1

©

60

58

60

65

12

©

55

50

65

60

13

©

55

50

60

50

14

O

60

55

65

60

15

9

60

55

16

©

55

50

65

60

Coaparative

Example 5

A

40

25

60

70

6

A

30

.15

60

55

7

X

35

20

70

65

JK 40T: X 20 days

16

GB2 180841A 16

Claims

1. An aqueous coating composition comprising carboxyl bearing resinous powder (I), basic compound (II), aqueous resin (III) and optional compound which is mutually reactive with (I)

and/or (III), the amount of said basic compound (II) corresponding to 0.3 to 1.2 equivalent to

5 the total amounts of carboxyl groups of (I) and (III) and solid weight ratio of (I): (III) being 2:98 5 to 98:2, which is characterized in that at least 20% of said basic compound (II) is a member having a boiling point of more than 150°C.

2. A composition as claimed in claim 1, wherein the basic compound (II) is a member having a boiling point of 150-400°C.

10

3. A composition according to claim 1, substantially as herein described in any of the 10

foregoing Examples.

Printed for Her Majesty's Stationery Office by Burgess & Son (Abingdon) Ltd, Dd 8991685, 1987.

Published at The Patent Office, 25 Southampton Buildings, London, WC2A 1 AY, from which copies may be obtained.